When the first quantum computers are realized, they will be room-sized, super-cooled and incredibly expensive. Most of the organizations wanting to utilize the unique capabilities of these machines won’t have one of their own sitting in the server room.

Initially then, businesses will likely purchase runtime on quantum computers, and interact with it remotely over the internet.

Given the sensitive and confidential nature of the data and programs businesses will want to run on quantum computers – the issue of security is already rearing its head.

Until recently, it was thought to be impossible to maintain private interactions with quantum computers, unless the user had their own quantum network.

But in a paper published this month in Physical Review X, researchers from RMIT University, National University of Singapore and Singapore University of Technology and Design have presented a “tantalizing possibility that it may be possible for a classical user to hide a computation from a quantum server”.

Spinning blind

Users wanting to perform computations on a remote quantum computer are faced with two main security concerns that need to be overcome, the researchers say.

“The privacy concern is that the description of their computation, both the program and any input data, remains hidden even from the server. The correctness concern is that a malicious server might tamper with their computation, sending them a misleading result; hence, ideally such behavior would be detectable,” RMIT’s Dr Nicolas Menicucci et al write in their paper Flow ambiguity: A path towards classically driven blind quantum computation.

What’s needed are ‘blind quantum computing protocols’. While these have been proposed in previous research, until now they have required that at least two parties possess quantum capabilities.

“Removing this requirement and allowing a purely classical user to interact with a single quantum server would greatly expand the practicality of delegated quantum computation,” the researchers say.

The protocol suggested by the paper’s authors “exploits the ambiguity” in the flow of information in a measurement-based quantum computer.

The method means quantum computer can't tell which qubits were used for inputs, which for operations and which for outputs. The sheer number of possible sequences also protects from any reverse engineering attempts.

The result “allows the tantalizing possibility that it may be possible for a classical user to hide a computation from a quantum server”.